The invention concerns an emergency operation ring for tubeless pneumatic tires in motor vehicles which have two or multi-component rims. The ring has a base section which rests on the rim and at least one circumferential groove which faces the inner wall of the tire tread and contains a slipping agent. In intact pneumatic tires, the groove or grooves are held closed by initial axial tension. At least one of the sealing lips of the groove or grooves forms the working arm of a lever-like circumferential support section. At the beginning of emergency operations, the support section is subject to a pressure increase due to the wheel load transferred to it by the tire cover. The sealing lip connected to the support section is thus lifted from the groove, thereby releasing the slipping agent which functions to lubricate the surfaces of the pneumatic tire in contact with the emergency operation ring.
An emergency operation ring of the above-named type is disclosed in applicants' U.S. Pat. No. 4,371,024, granted Feb. 1, 1983. In the known ring, the entire height of the sides, the base section as well as the upper section, fits against the pneumatic tire. The known ring extends in a dome-shape from the side edges of the upper section to the central plane of the ring. Because of its construction, the known ring has a relatively large volume and a correspondingly high weight. Even a vehicle equipped with only four wheels is considerably burdened by the high weight of the ring, and its road handling is noticeably impaired. This disadvantage is particularly great with larger wheel dimensions. Aside from this, the voluminous ring works as a heat accumulator whose heat energy increases considerably with progressively longer periods of driving. This adversely effects the temperature of the compressed air in the tire as well as the material of the pneumatic tire. Finally, the outer flanks of the ring are in contact with the pneumatic tire along their entire surface area in intact tires. This creates the disadvantage that the surfaces in contact are subject to more or less heavy friction, depending on the air pressure, with corresponding wear.